The present invention relates to a double-layered rubber laminate or, more particularly, to a double-layered rubber laminate consisting of integrally laminated cured rubber layers of different types of rubber compositions.
Needless to say, various types of rubbers each have different chemical and physical properties and each of them has its own merits and demerits so that it is sometimes required that an article shaped from a cured rubber material have a laminate structure consisting of two layers of which one of the layers is formed from a rubber composition of a type different from that of the other layer when one of the surfaces of the rubber article is exposed to an ambient condition different from that to which the other surface of the article is exposed. In a rubber oil hose running within the engine room of an automobile, for example,it is essential that the inner surface of the hose in direct contact with an oil be highly oil-resistant while the outer surface of the hose, which receives the heat radiation from the high-temperature engine, be highly heat resistant. Further, laminated rubber bodies consisting of layers of, one, an electroconductive rubber and, the other, an insulating rubber are widely used in electronic instruments as a rubber contact. It is sometimes required that a coating layer of rubber provided on a substrate surface be laminate consisting of a top layer having high weatherability and an underlying layer which is highly susceptible to adhesive bonding to the substrate surface.
One of the problems common in these rubber laminates is that the bonding strength between the rubber layers of different types is not always very firm and reliable so that partial peeling or delamination of the layers is unavoidable even in the products as manufactured, resulting in a decreased yield of acceptable products, if not to mention the disadvantage in such a product that the serviceable life thereof is not long enough due to separation of the layers during use.